A phacoemulsification surgical instrument provides for the breaking apart and the removal of unwanted tissue and material, especially a cataract located in the anterior chamber of the eye, by ultrasonically fragmenting the cataract while simultaneously introducing fluid into the eye chamber and withdrawing the fluid and fragmented cataract particles. A phacoemulsification instrument includes a handpiece having an operative needle vibrating in the ultrasonic range. The needle shaft is hollow and is in turn surrounded by a tubular sleeve. In operation, the needle shaft including the surrounding tubular sleeve is inserted into the anterior chamber of the eye. Irrigation fluid is introduced through the hollow sleeve to provide a replacement for fluid withdrawn or lost from the eye chamber during surgery. The needle tip is used to emulsify the cataract.
It is desirable to emulsify the lens nucleus in situ because removing the nucleus from its original position and emulsifying the nucleus elsewhere in the eye creates a possibility of damage to other eye tissue, such as damage to the iris and corneal endothelium. However, emulsification of the lens in situ causes additional problems, particularly the danger of rupturing the posterior capsule. If the posterior capsule encounters a sharp instrument, particularly a vibrating needle, the posterior capsule may be easily punctured, and once its structural integrity is broken, the posterior capsule generally splits and tears. Damage to the posterior capsule results in the loss of vitreous humor and lens particles and other material falling into the posterior chamber resulting in undesirable complications, dangers and difficulties in performing cataract surgery and patient recovery.
A need has thus arisen for a phacoemulsification needle having a tip which greatly reduces the probability of posterior capsule rupture, especially when the lens is emulsified in its original position.